Lead screw device, lens driver, lens barrel, and camera using the lead screw device

An optical device comprising:

• an optical system including a plurality of lens groups, at least one lens group of the plurality of lens groups being a movable lens group capable of moving in an optical axis direction of the optical system;
• and
• a movable frame configured to move the movable lens group,
• the movable frame including:
• a driving source;
• a drive screw driven by the driving source;
• a lens supporting frame configured to support the movable lens group and maintaining an integrated state relative to the movable lens group;
• a plurality of arms separate from the lens supporting frame and disposed in a position to face the drive screw and being openable and closable relative to the drive screw with a single opening and closing axis as a support axis, the plurality of arms including a first arm and a second arm;
• and
• a first biasing spring configured to apply a first biasing force to the first arm in a direction in which the first arm approaches the drive screw.